A. Field of the Invention
The present invention relates to a new arrangement for a slip spring for downhole tools such as packer tools, retrievable bridge plugs or the like.
B. Description of the Prior Art
In order to insert, set and retrieve packer tools and similar devices, complex arrangements of shear pins, springs, J tools, slips and drag blocks have been developed so that the packer tools or other devices can be reused. The drag blocks and slips must be able to selectively engage the inner wall of the well bore so that the tool can be set or unset, often by rotating the tool to either shear a pin, engage or disengage a J tool or by compressing or expanding the tool to lock or unlock. This is well known as shown for example in U.S. Pat. No. 5,197,547 to Morgan. The slips 62 in the Morgan patent are activated as the annular tapered surface 61 slides (“wedges”) behind the slips 62 forcing them outwardly until engage the well bore.
Prior to the current invention, complex casings were developed to retain the springs and slips in place during installation and run in. As shown in FIGS. 1 and 2, casing 210 has a number of partitions 212 machined or welded into the casing. Slots 214 provide a registration point for the slips 216 and allow the base of the slips to rotate free of the casing wall. The upper portion protrudes from above the casing and are held within the outer diameter of the casing wall by a retaining spring 218 (FIG. 2A) which urges the slip inwardly from the casing wall. The partition 212 is necessary to hold the spring 218 inside the pocket 220 provided along the length of the slip 216 since the pocket 220 has no sides to retain the spring. It is also usually necessary to weld or machine lugs along the inner portion of the partitions to further locate and center the springs securely within the slip.
The current invention provides a self-centering spring engageable with a slip modified according to the present invention. A groove located at a lower center of the slip below the pocket of the slip cooperates with the spring to retain the spring against the slip and centered within the pocket without requiring the partitions or further welding of lugs to retain the springs.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.